. my arms are 15", im 158 lb OP and only been training for 3-4 months.. so idk if your arms aare good
. Judging by your picture you build is different to mine. Your arms would have been naturally bigger then mine. When i started i was a stick.
. Considering you said you had been going to the gym for 7 months and have a 12kg gain, tends to lead me to believe you have gained a lot of fat. That's 3.7lbs per month. That's a lot and not necessarily a good thing.